I upgraded my 4870x2 (two cards) in crossfire setup to a 5970 in crossfire (also two cards) and the major blow here is that the fans on both of the Sapphire cards is making a very anoying rattling sound.. The web is full of complaints about the fans on literally ANY vendors 5970 version, I think it has something to do with the reference design (poor fan?)

I tore out the cards, and opened one of them (yes, I work HW on daily basis, so I THINK (just maybe ) I know what I'm doing.. lol..

Well, after 15 small bolts, then three even smaller, then 8 "big" after removing the print I finally came to the inner core of the fan, and checked if it where loose somehow. The three bolts holding it, were pretty tight, but I found that that a tiny little plastic "bolt" was a micrometer above the flat plastic cover and tought this might touch the fan when spinning. (argh, hard to explain) However, I cut it even with the plastic cover using a stanley, and then I carefully asembled the card again.

The thing is, that the fan it self drops down three millimeters when it's standing inside the cabinet. If you have the card horizontal, it doesn't make any sound at all (except from expected fan blow sound).

So, asembled it was, and I put the one card back to have a try. The sound was gone!... for three minutes, then it came back, but this time alot more silent, yet still quite annoying..

And, it goes for every vendor; Sapphire, PowerColor, XFX and so on.. damn this thingy is driving me insane! heh..

I'll try once more time, leaving me without any warranty, but heck, if it doesn't work, I'll buy the "freezer" from AC when it's ready. Until then, I'll just have to turn up the volume on the sound output

My Saphire OC has it as well. I think it may be getting quieter or I could just be getting used to it. I was advised by sapphire to rma it if I wanted to but they did not seem concerned about it. It is definately to do with the fan droping gently pushing the fan up just a tiny amount stops the sound straight away. AC cooler asap!

I can imagine that the weight of the magnet inside the 'rotor' (the piece of the fans motor, with the blades on it) is affected by gravity, pulling it out of natural 'center' position. If the fan is idle (low speed) the centrifugal force created by the speed isn't strong enough to keep the rotor in its original position.

Just like poo417 discribes as he's pushing the rotor upwards (to its original 'center'), the sound will at least for a small amount decrease.

So If you'd place the card upside down like in a BTX setup, the rotor isn't pulled out of its designed center position.

Its just a thought though

My HD2900XT had the same problem. I believe the fan used in the 5970 is the same as that of the 2900XT/Pro.

\\EDIT: Just re-read your post and I guess I know what you mean with "tiny little plastic bolt". Its the washer that 'clicks' around the rotor's axle to keep the rotor in-its-place. With the 'washer' removed you can pull out the rotor completely I presume?

my 4870 started to have that sound too
it starts at windows start up, when overdrive pushes fan to 35%, but after a couple minutes its gone.
I thought fan needed oil or something... just afraid that the fan will die one day